Method and system for electrical and mechanical power generation using Stirling engine principles

ABSTRACT

A heat engine enclosed in a housing has two chambers maintained at different temperatures. The first chamber (“hot chamber”) receives heat energy from an external power source. The second chamber (“cold chamber”) is connected to the hot chamber by two conduits, such that a fluid (e.g., air, water, or any other gas or liquid) filling the two chambers can circulate between the two chambers. The expansion of the fluid in the hot chamber and the compression of the fluid in the cold chamber drive a turbine to provide a power output. The fluid may be pressurized to enhance efficiency. In one embodiment, the turbine propels an axle in a rotational motion to transmit the power output of the heat engine to an electrical generator outside of the heat engine&#39;s housing. In one embodiment, the turbine includes a first set of blades and a second set of blades located in the hot chamber and the cold chamber, respectively. The blades may each have a flat profile having two unequal surfaces, such that the turbine rotates in preferentially in one direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to applying Stirling engine principles to the design and use for power conversion equipment. In particular, the present invention relates to applying Stirling engine principles for electrical and mechanical power generation, especially in the direct current (DC) mode or in the alternating current (AC) modes.

2. Discussion of the Related Art

The Stirling engine is a heat engine that operates by converting the heat energy which flows between two portions of the heat engine having different temperatures into mechanical power. A typical Stirling engine uses the heat energy to drive a coordinated and reciprocating motion of a set of pistons. Numerous designs of Stirling engines can be found in the prior art, including: U.S. Pat. Nos. 6,578,359, 6,050,092, 6,195,992, 6,735,946 and 6,164,263. The designs of these Stirling engine are typically complex and include numerous moving parts. Consequently, these designs are costly to manufacture and their efficiencies are low.

SUMMARY

The present invention provides a heat engine enclosed in a housing having two zones maintained at different temperatures. The first zone (“hot zone”) receives heat energy from an external power source. The second zone (“cold zone”) is connected to the hot zone, such that a fluid (e.g., air, water, or any other gas or liquid) filling the two zones can circulate between the two zones. The expansion of the fluid in the hot zone and the compression of the fluid in the cold zone provide a symmetrical thermodynamic cycle to drive a turbine to provide a power output. The fluid may be pressurized to enhance efficiency.

In one embodiment, the turbine propels an axle in a rotational motion to transmit the mechanical power output of the heat engine. In one embodiment, the turbine propels an axle in a rotational motion to transmit the power output of the heat engine to an electrical generator outside of the heat engine's housing. In one embodiment, the turbine includes a first set of blades attached to a plate located in the hot zone and a second set of blades attached to a plate located in the cold zone. The blades may each have a flat profile having two unequal surfaces, such that the turbine rotates in preferentially in one direction. In one embodiment, the electrical generator includes one or more magnets in rotational motion according to the rotational motion of the axle, and one or more conductive coils coupled to the magnetic fields of the one or more magnets. The amount of coupling between the magnets and the coils may be controlled by a step motor moving the coils into different positions relative to the magnets. In one embodiment, the electrical generator delivers AC power. Alternatively, DC power may be provided by either rectifying the AC power, or by selectively coupling those coils that have an instantaneous positive voltage relative to a ground terminal. To synchronize the coil selection, a position sensor may be provided to sense the positions of the magnets. In one embodiment, the position sensor includes a light sensitive sensor, a light emitting diode and a light reflector.

According to one embodiment of the present invention, a temperature sensor may be used to control the power output of the heat engine. A signal output of the temperature sensor indicates a temperature difference between the hot and cold chambers. Based on this output signal of the temperature sensor, a control circuit adjusts the coupling between the magnets and the coils in the electrical generator. In an AC power generation application, a control circuit senses to the frequency of the electrical generator's output power to control the output power of the electrical generator.

In one embodiment, adding power output is achieved using thermal couples and thermionic devices. The thermal couple takes advantage of the temperature difference between the hot and cold chambers. The thermionic devices extract heat from the housing of the heat engine. These devices may be stored in an insulated chamber between two plates separating the hot and cold zones.

The present invention provides a heat engine in which the gas or fluid transferring heat between the hot and cold zones is used to drive the turbine, resulting in low power loss in the energy conversion process. In addition, the housing provides air flow between the hot zone and the cold zone through a center shaft and a peripheral space so as to allow 100% component use with no dead time. The cylindrical symmetry of the heat engine provides stability with minimum vibration and an absence of drag during operation. The heat engine of the present invention has a simple design with few moving parts, without the requirements of a displacer, a piston or a regenerator. Thus, the heat engine of the present invention is light weight, low component cost and easy to maintain.

A heat engine of the present invention may be used to power an automobile or another vehicle. It can also be incorporated, for example, in any application in which a source of heat energy is provided (e.g., fuel cells or energy recovery from combustion of waste).

In addition, the control system of the present invention provides a consistent output power to enhance fuel efficiency.

The present invention is better understood upon consideration of the detailed description below and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows heat engine 100 receiving solar energy from a solar reflector 160, in accordance one embodiment of the present invention.

FIG. 2 shows one implementation of heat engine 100 of FIG. 1 in a cross-sectional view.

FIG. 3 represents both the cross-sectional view of heat engine 100 along line B-B′, viewed from top, and the cross-sectional view of heat engine 100 along line C-C′, viewed from the bottom.

FIG. 4 is a cross section view of heat engine 100 along line D-D′, showing center axle 101, magnets 108 and coils 109.

FIG. 5 shows control circuit 501 capable of controlling the output power based on an operating temperature difference.

FIG. 6 shows multiplexing switch 601 provided to selectively couple each of terminal x to output terminal y.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a heat engine, operating under Stirling engine principles, for converting heat energy into mechanical and electrical energy. The electrical energy derived using a heat engine of the present invention may be in the form of alternating current (AC) power, for immediate distribution, or in the form of direct current (DC) to allow storage or other applications.

The heat engine of the present invention may operate with any source of heat energy, including solar, geothermal, fossil, landfill recovered or other fuels. FIG. 1 shows heat engine 100 receiving solar energy from a solar reflector 160, in accordance one embodiment of the present invention. One embodiment of heat engine 100 of FIG. 1 is shown in a cross section view in FIG. 2. As shown in FIG. 2, heat energy 100 includes an external housing 107 which seals a hot portion or zone 107 a and a cold portion or zone 107 b. In this detailed description, the terms “hot” and “cold” are relative. A heat engine of the present invention will operate as long as there is a sufficient temperature difference between the hot portion and the cold portion. Further, the upper and lower portions of FIG. 2 are labeled “top” and “bottom”, respectively, merely to facilitate reference in this detailed description. A heat engine of the present invention is not limited by its position in any orientation.

Hot portion 107 a (“hot zone”) and cold portion 107 b (“cold zone”) are insulated from each other by insulating zone 106. Except for insulating zone 106, housing 107 may be metallic (e.g., steel) to allow rapid and even heat distribution. Heat engine 100 includes turbine 103; in the implementation shown in FIG. 2, turbine 103 includes two sets of blades, labeled 103 a and 103 b, respectively, which are connected by center axle 101. Blade set 103 a and blade set 103 b are housed within the hot and cold zones, respectively. Blade sets 103 a and 103 b are preferably made of metal to allow even and rapid heat distribution. In this embodiment, blade sets 103 a and 103 b are provided on support plates 114 and 115 respectively.

FIG. 3 represents both the cross-sectional view of heat engine 100 along line B-B′, viewed from top, and the cross-sectional view of heat engine 100 along line C-C′, viewed from the bottom. In relation, the cross-sectional view of FIG. 2 represents a cross-section along line A-A′ of FIG. 3. Blade sets 103 a and 103 b are each provided a rounded contour, such that one side of the blade has a larger cross-section than the other, to allow the blades to rotate in a predetermined direction. The difference in surface area is not necessary, but may provide some advantage in some applications, such as ease in starting up. Blade sets 103 a and 103 b provide large surface areas for heat transfer. Thus, heat engine 100 has a high surface to volume ratio to enhance efficiency.

Center axle 101 is unsheathed in air shaft 102 that runs from top to bottom along the entire lengths of hot portion 107 a and cold portion 107 b of housing 107, connecting the hot and cold chambers. The hot and cold zones are also connected by annular space 104 along the circumference of the outer wall of housing 104. Center axle 102 is held by bearings 105, which allow center axle 101—and thus blade sets 103 a and 103 b also—to rotate about its center axis. Because the contact points between bearings 105 and center axle 103 are the only locations in heat engine 100 which experience mechanical wear and tear, heat engine 100 has a long service life and a low service requirement and thus easily maintained. A portion of center axle 101 extends outside of housing 107. Cylindrical magnet 108 attaches to and rotates with this portion of center axle 101 which extends outside of housing 107. One or more coils 109 surround magnet 108. Coils 109 may be driven by step motor 110 in an up and down motion to vary the amount of magnet flux coupling the magnetic field of magnet 108. FIG. 4 is a cross sectional view of heat engine 100 along line D-D′, showing center axle 101, magnet 108 and coils 109. As shown in FIG. 4, coils 109 may include one or more coils with their respective output terminals (labeled “x”) and a common ground terminal. FIG. 2 also shows reflector 111 provided with magnet 108, and a position sensor 112. Position sensor 112 includes a light emitting diode (LED) and a sensor sensitive to light reflected from reflector 111. Each of coils 109 may be provided with a position sensor, so that a control circuit may be able to determine the frequency and the phase of the alternating electrical current induced in the coil by the magnet.

In this embodiment, when coils 109 includes more than one coil (as may be desirable for DC power generation), a multiplexing switch 601 may be provided, as shown in FIG. 6, to selectively couple each of terminal x to output terminal y according to the phase of the alternating electrical current in each coil. If only one coil is present in coils 109, the single output terminal x of coils 109 is directly coupled to terminally.

During operation, as heat builds up in hot portion 107 a of housing 107, the expanding air in the hot zone rises and pushes against blade set 103 a on support plate 114. Thus, turbine 103 begins to rotate about the axis of center axle 101 due to the torque of the expanding air. The expanding air moves radially outward towards the periphery and into the cold zone via annular air space 104. As the expanding air enters into cold zone 107 b, the air in cold zone 107 b contracts by a cooling mechanism (e.g., the walls of housing 107 in cold zone 107 b may include pipes circulating a cooling fluid). The contracting air draws the expanding air into cold zone 107 b. As blade set 103 b on support plate 115 in cold zone 107 b is connected by center axle 101 to rotating blade set 103 a on support plate 114, blade set 103 b rotates at the same angular speed as blade set 103 a, thereby contributing to the torque rotating turbine 103. The cooled air in cold zone 107 b is drawn by convection radially towards center axle 101 and is forced into hot zone 107 a via air shaft 102. Thus, a circulation of air is established which flows radially outwards in hot zone 107 a, enters cold zone 107 b via annular airspace 104, flows radially inwards in cold zone 107 b and returns to hot zone 107 a through air shaft 102. In this process, the relatively hot air from hot zone 107 a that expands and flows into cold zone 107 b is cooled in cold zone 107 b, while the relatively cold air from cold zone 107 b is heated in hot zone 107 a. As magnet 108 rotates with center axle 101, the result varying magnetic field induces one or more electrical currents in coils 109. This electric current can be used to generate AC or DC electrical power, as discussed in further detail below. A temperature difference between hot zone 107 a and cold zone 107 b may be established, such that the output power and the heat dissipated from housing 107 equals the input power. Cold zone 107 b may be cooled and maintained at a pre-determined temperature by fluid (e.g., air). Such fluid may flow in channels provided in walls of housing 107 b, or by other means known to those skilled in the art. Efficiency for the heat transfer may be enhanced by pressurizing the hot and cold zones. Alternatively, rather than using air, other gases may also be used.

The operating temperature difference between hot zone 107 a and cold zone 107 b either by the cooling method discussed above, by controlling the output power, or both. The output power can be controlled by increasing or decreasing the magnetic field coupling between magnet 108 and coils 109 by motor 110 driving coils 109 up or down. A temperature sensor (not shown) sensitive to the temperature difference between hot zone 107 a and cold zone 107 b may be provided to sense the operating temperature difference. FIG. 5 shows control circuit 501 capable of controlling the output power based on the operating temperature difference. The control scheme may be implemented using digital or analog techniques, as known to those skilled in the art. As shown in FIG. 5, a signal v representing the operating temperature difference is received from the temperature sensor and provided to control circuit 501. Based on the value of signal v, output control signal w drives step motor 110 up or down to vary the magnetic coupling between magnet 108 and coils 109, as appropriate.

For generating AC electrical power, position sensor 112 may be used to detect the rotational frequency of axle 101. Positional sensor 112 asserts a control signal (e.g., control signal t) to control circuit 501 whenever reflector 111 comes into the detection field of positional sensor 112. The time difference between successive assertions of the control signal allows control circuit 501 to determine the frequency of the rotating magnetic field of magnet 108, and thus the frequency of the output AC power.

As mentioned above, for AC power generation, coils 110 need only be a single coil, output terminal y is a single output. Without further processing, the output power is delivered in the form of an AC current flowing between terminal y and the ground terminal, whose frequency is proportional to central axle 101's angular speed of rotation. Because the amount of output power is a load on center axle 101, increasing the amount of magnetic coupling between magnet 108 and coils 109 increases the load on center axle 101, thereby affecting the angular speed of rotation. Accordingly, the output terminal y may be coupled into a high impedance input terminal of control circuit 501, which may be provided a frequency sensing circuit (e.g., a trigger circuit). The detected frequency of the output AC current is used to adjusted through step motor 110, which drives coils 109 up or down according to output control signal w. This control scheme may thus be used to provide an output power from heat engine 110 which is compatible with 50 or 60 Hz household AC power.

In DC power generation, coils 110 may include multiple coils. At any given time, some of terminals x have positive voltages relative to the ground terminal, and others of terminals x have negative voltages relative to the ground terminal. During DC power generation, the position sensor associated with each of coils 109 provides to control circuit 501 control signal t which indicates when the associated reflector comes into the detection field of the position sensor. Once the particular coil of coils 109 is identified as having the desired positive voltage phase, control circuit 501 provides control signals z to switch 601 (FIG. 6) which selectively couples output terminal x of the particular coil to output terminal y. In this manner, DC power generation is accomplished. The signal in output terminal y may be shaped to a constant voltage using, for example, a low-pass filter or a voltage regulator.

Alternatively, the AC output power generated according to discussion above may be rectified to provide a DC power output, using any suitable rectifier circuits known to those skilled in the art.

Additional energy conversion may be accomplished using thermal couples that provide output signals according to the temperature difference between hot zone 107 a and cold zone 107 b. Alternatively, the walls of housing 107 at hot zone 107 a may be used to generate power using thermionic principles. The thermal couples or thermionic components can be housed insulating zone 106 of FIG. 1, for example.

The above detailed description is provided to illustrate the specific embodiments of the present invention and is not intended to be limiting. Numerous modifications and variations with in the scope of the present invention are possible. The present invention is set forth in the following claims. 

1. An apparatus for power generation, comprising: a housing enclosing a fluid, the housing receiving heat energy from a power source; a first zone in the housing coupled to receive the heat energy; a second zone in the housing isolated from the first zone and dissipating heat away from the housing, such that a temperature difference is created between the first zone and the second zone; and a turbine having a portion in the housing which is put into rotational motion by fluid expansion and compression due to the temperature difference.
 2. An apparatus as in claim 1, wherein the turbine includes an axle driven by the rotational motion.
 3. An apparatus as in claim 1, wherein the housing has a toroidal shape.
 4. An apparatus as in claim 1, wherein the turbine has a first set of blades located in the first zone.
 5. An apparatus as in claim 4, wherein the first set of blades is supported by a support plate.
 6. An apparatus as in claim 1, wherein heat dissipation from the second zone is accomplished by circulating a fluid.
 7. An apparatus as in claim 1, wherein the fluid flows between the first zone and the second zone through a first space at the periphery of the housing and a second space between the first zone and the second zone.
 8. An apparatus as in claim 1, wherein the fluid comprises air.
 9. An apparatus as in claim 1, where in the fluid is pressurized.
 10. An apparatus as in claim 4, wherein each blade in the first set of blades has a first surface and a second surface, the first surface and the second surface of each blade having unequal surface areas, such that the first set of blades rotate in a predetermined rotational direction.
 11. An apparatus as in claim 2, further comprising an electrical generator having a magnet in rotational motion according to the rotational motion of the axle, and one or more conductive coils coupled to the magnetic fields of the magnet.
 12. An apparatus as in claim 11, wherein the amount of coupling between the magnet and the coils is controlled by a step motor moving the coils into different positions relative to the magnets.
 13. An apparatus as in claim 11, wherein the electrical generator delivers AC power.
 14. An apparatus as in claim 11, wherein a position sensor is provided to sense a position of the magnet, the sensed position being used to select one of the coils having a positive voltage across its terminals for output.
 15. An apparatus as in claim 14, wherein the position sensor comprises a light sensitive sensor, a light emitting diode and a light reflector.
 16. An apparatus as in claim 11, further comprising a temperature sensor which outputs a signal indicating a temperature difference between the first zone and the second zone, the output signal of the temperature sensor being used to control the output power of the electrical generator.
 17. An apparatus as in claim 11, further comprising a control circuit which responds to the frequency of an output signal of the electrical generator to control the output power of the electrical generator.
 18. An apparatus as in claim 1, further comprising a thermal couple providing a power output based on the temperature difference between the first zone and the second zone.
 19. An apparatus as in claim 1, further comprising a thermionic device providing a power output using heat from the housing.
 20. An apparatus as in claim 18, wherein the thermal couple is placed between the first zone and the second zone.
 21. A method for power generation, comprising: enclosing a fluid in a housing which receives heat energy from a power source; coupling the heat energy to a first zone in the housing; isolating a second zone in the housing from the first zone and dissipating heat away from the housing, such that a temperature difference is created between the first zone and the second zone; and providing a turbine having a portion in the housing which is put into rotational motion by fluid expansion and compression due to the temperature difference.
 22. A method as in claim 21, further comprising including in the turbine an axle driven by the rotational motion.
 23. A method as in claim 21, wherein the housing is provided a toroidal shape.
 24. A method as in claim 21, wherein the turbine has a first set of blades located in the first zone.
 25. A method as in claim 24, wherein the first set of blades is supported by a support plate.
 26. A method as in claim 21, wherein heat dissipation from the second zone is accomplished by circulating a fluid.
 27. A method as in claim 21, further comprising providing a first space at the periphery of housing and a second space between the first zone and the second zone so as to allow fluid to move between the first zone and the second zone.
 28. A method as in claim 21, wherein the fluid comprises air.
 29. A method as in claim 21, where in the fluid is pressurized.
 30. A method as in claim 24, further comprising providing each blade in the first set of blades a first surface and a second surface, the first surface and the second surface of each blade having unequal surface areas, such that the first set of blades rotates in a predetermined rotational direction.
 31. A method as in claim 22, further comprising providing an electrical generator having a magnet in rotational motion according to the rotational motion of the axle, and one or more conductive coils coupled to the magnetic fields of the magnet.
 32. A method as in claim 31, wherein the amount of coupling between the magnet and the coils is controlled by a step motor moving the coils into different positions relative to the magnets.
 33. A method as in claim 31, wherein the electrical generator delivers AC power.
 34. A method as in claim 31, further comprising providing a position sensor to sense a position of the magnet, the sensed position being used to select one of the coils having a positive voltage across its terminals for output.
 35. A method as in claim 34, wherein the position sensor comprises a light sensitive sensor, a light emitting diode and a light reflector.
 36. A method as in claim 31, further comprising providing a temperature sensor which outputs a signal indicating a temperature difference between the first zone and the second zone, the output signal of the temperature sensor being used to control the output power of the electrical generator.
 37. A method as in claim 31, further comprising providing a control circuit which responds to the frequency of an output signal of the electrical generator to control the output power of the electrical generator.
 38. A method as in claim 21, further comprising providing a power output from a thermal couple based on the temperature difference between the first zone and the second zone.
 39. A method as in claim 21, further comprising providing power output from a thermionic device using heat from the housing.
 40. A method as in claim 38, further comprising placing the thermal couple between the first zone and the second zone.
 41. An apparatus as in claim 1, wherein the turbine has a second set of blades located in the second zone.
 42. An apparatus as in claim 41, wherein the second set of blades is supported by a support plate.
 43. An apparatus as in claim 41, wherein each blade in the second set of blades has a first surface and a second surface, the first surface and the second surface of each blade having unequal surface areas, such that the second set of blades rotates in a predetermined rotational direction.
 44. A method as in claim 21, wherein the turbine has a second set of blades located in the second zone.
 45. A method as in claim 44, wherein the second sets of blades is supported by a support plate.
 46. A method as in claim 44, further comprising providing each blade in the second set of blades has a first surface and a second surface, the first surface and the second surface of each blade having unequal surface areas, such that the second set of blades rotates in a predetermined rotational direction.
 47. An apparatus as in claim 5, further comprising means for applying heat to the first sets of blades and its support plate.
 48. An apparatus as in claim 42, further comprising means for cooling the second sets of blades and its support plate.
 49. An apparatus as in claim 5, further comprising a thermal insulation zone.
 50. An apparatus as in claim 49, further comprising a thermal-electric device.
 51. An apparatus as in claim 1, wherein the fluid circulates in the open space between the first zone and the second zone within said housing.
 52. An apparatus as in claim 1, wherein the fluid circulates over a non-linear path.
 53. An apparatus as in claim 1, wherein the fluid circulates in a plurality of paths between the first zone and the second zone.
 54. An apparatus as in claim 4, wherein the motion of the turbine provides an evenly distributed torque on the axle.
 55. A method as in claim 25, further providing a thermal insulation zone.
 56. A method as in claim 55, further providing a thermal-electric device for electricity generation.
 57. A method as in claim 21, wherein the fluid circulates over a radial path between the first zone and the second zone.
 58. A method as in claim 21, wherein in the fluid circulates between the first zone and the second zone over a non-linear path.
 59. A method as in claim 21, wherein the fluid circulates over a plurality of paths between the first zone and the second zone within said housing.
 60. A method as in claim 21, wherein the motion of the turbine provides an evenly distributed torque on the axle.
 61. A method of providing working fluid circulation path through space within an enclosed housing of a heat engine, the method comprising: providing a turbine within the housing; partitioning the housing into to a first zone and a second zone; filling the housing, including the first zone and the second zone, with the working fluid; heating said first zone with the heat from a heat source; and cooling said second zone using said heat sink to dissipate the heat.
 62. A method for mechanical power generation using a heat engine with an enclosed housing, the method comprising: partitioning the housing into a first zone and a second zone, the first zone further adapted from receiving heat from a heat source, and the second zone being further adapted for transferring heat into a heat sink; providing a turbine having a set of blades supported on a first support plate and coupled to drive an axle supported on the first support plate. providing a working fluid in the first and second zones, wherein when heat is received from the heat source, the working fluid expands and urges the first set of blades, resulting in a rotational motion in the turbine, thereby providing power to drive the axle.
 63. A method as in claim 62, the method further comprising a second set of blades in the second zone, wherein when the working fluid is compressed in the second zone, the working fluid urges the second set of blades to result in rotational motion in the second set of blades.
 64. A method for generating mechanical power using a heat engine having a sealed housing filled with a fluid, the method comprising: providing a rotatable support plate connected to an axle, thereby partitioning the housing into a heat source zone and a heat sink zone; and providing a first set of blades on the support plate in said heat source zone, wherein the first set of blades are shaped such that expansion of the fluid in the heat source zone applies a force on the first set of blades, resulting in the torque for rotating the axle in a predetermined direction.
 65. A method as in claim 64, further comprising providing a second set of blades in the heat sink zone, wherein the second set of blades are shaped such that compression of the fluid in the heat sink zone applies a force on the second set of blades, contributing to the torque for rotating the axle.
 66. A method as in claim 64, further comprising providing a thermal insulation zone between the heat source zone and the heat sink zone.
 67. A method as in claim 64, further comprising providing power output from a thermionic device using heat from the housing.
 68. A method as in claim 64, further comprising placing a thermal couple between the heat source zone and the heat sink zone.
 69. A method as in claim 66, further comprising providing a thermal-electric device for electricity generation.
 70. A method of enhancing the output power of an electrical generator driven by a rotational motion of a device, the method comprising: calibrating a performance table relating a temperature difference in the device to an amount of magnetic coupling in a control device within the electrical generator, the amount of magnetic coupling being indicative of the maximum output power of said generator at that temperature difference; detecting the temperature difference using a temperature sensor in the device; obtaining from the performance table the amount of magnetic coupling corresponding to the temperature difference; and setting the control device to that amount of magnetic coupling.
 71. A method of claim 70, wherein the amount of magnetic coupling is represented by the position of a coil relative to a magnet.
 72. A method as in claim 70, wherein the control device communicates with a step motor moving the coil to the desired position.
 73. A method of enhancing the output power of an electrical generator from the rotational motion of a device, the method comprising: calibrating a performance table relating a rotational speed of the device to an amount of magnetic coupling in a control device within the electrical generator, the amount of magnetic coupling being indicative of the maximum output power of said generator at that temperature difference; detecting the rotational speed using a rotational speed sensor in the device; obtaining from the performance table the amount of magnetic coupling corresponding to the rotational speed; and setting the control device to that amount of magnetic coupling.
 74. A method of claim 73, wherein the amount of magnetic coupling is represented by the position of a coil relative to a magnet.
 75. A method as in claim 73, wherein the control device communicates with a step motor moving the coil to the desired position.
 76. A method of operating a heat engine exposed to a heat source, the heat engine having an enclosed housing configured a working fluid space, a first zone and a second zone, the first zone and the second zone having a temperature difference therebetween, the method comprising: moving the working fluid in the first zone towards a first portion of the working fluid space; moving the working fluid in the first zone through the first portion of the working fluid space into the second zone; moving the working fluid in the second zone towards a second portion of the working fluid space; and moving the working fluid in the second zone through the second portion of the working fluid space into the first zone.
 77. A method of operating a heat engine having an enclosed housing configured as a working fluid space, a heat source zone and a heat sink zone, the heat source zone having a higher temperature than the temperature in the heat sink zone, the method comprising: moving said working fluid from said heat source zone to said heat sink zone through a first portion of the working fluid space; and moving said working fluid from said heat sink zone to said heat source zone through a second portion of the working fluid space;
 78. A method of operating a heat engine having an enclosed housing configured as a working fluid space, a heat source on one side and a heat sink on the opposite side of the heat source, the method comprising: providing in said housing a hot zone with a higher temperature due to heat from said heat source and a cold zone with a lower temperature due to heat conducting away by said heat sink; circulating the working fluid between the hot zone and the cold zone through the working fluid space; and using the motion of the working fluid to turn a turbine so as to provide mechanical power.
 79. A method of operating a heat engine having an enclosed housing configured as a working fluid space, a heat source zone and a heat sink zone, the heat sink zone having a lower temperature than the temperature of the heat source zone, the method comprising: openly circulating said working fluid between said heat source zone and said heat sink zone; and using the motion of the working fluid to drive a turbine, so as to create a torque for generating mechanical power.
 80. A method of operating a heat engine having an enclosed housing configured as a working fluid space, a heat source zone and a heat sink zone, the heat source zone having a higher temperature than the temperature of the heat source zone, the method comprising: providing a plurity of fluid paths in the working fluid space for movement of the working fluid between said heat source zone and said heat sink zone; and using the motions of the working fluid in the fluid paths to rotate a turbine, so as to produce mechanical power.
 81. A method for operating a heat engine exposed to a heat source, the heat engine having an enclosed housing configured as a working fluid space, a first zone and a second zone, the first zone and the second zone having a temperature difference therebetween, the method comprising: moving the working fluid into a first portion of the working fluid space; moving the working fluid in the first portion of the working fluid space into the second zone; moving the working fluid in the second zone into a second portion of the working fluid space; and moving the working fluid in the second portion of the working fluid space into the first zone. 